Interpretive Summary: A simulated digestion/cell culture model for estimating bioavailable iron in foods was developed in 1996 and has been applied in many studies. However, the model has not been quantitatively validated with human trials. In this study, the model was compared to reported human trials on iron bioavailability. Ascorbic acid, a promoter of iron absorption, and tannic acid, an inhibitor of iron absorption exhibited effects very similar in pattern relative to that of human studies. Comparison of the effects of proteins on iron absorption yielded differences and similarities with human studies, but the results were inconclusive as some effects could be explained by differences in protein source and possibly experimental design. Based on our experimental results, it can be concluded that the simulated digestion/cell culture model can be used to rank foods with simple and similar food matrixes. To apply the model in mixed food with complicated food matrixes, further studies are needed.

Technical Abstract:
An in vitro digestion/Caco-2 cell model for estimating bioavailable iron in foods was developed in 1996 and has been applied in many studies. However the model has not been quantitatively validated with human trials. In this study, the model was compared to reported human trials on iron bioavailability. The dose response curve of the effect of ascorbic acid and tannic acid on iron uptake was shown to be in a very similar pattern in the Caco-2 model as that in human studies. The correlation coefficient between the absorption ratio with and without ascorbic acid or tannic acid in Caco-2 cell model and in the human trial is 0.9969 and 0.9828 respectively. The effect of bovine serum albumen on iron absorption in Caco-2 cell model was similar to that in human studies. The effect of substitution of casein for chicken egg albumin or deleting protein from semi-synthetic meal (SS) on iron bioavailability was different in Caco-2 cell model from that in human studies. However this difference can be explained by the differences in the source of casein and the study design between human studies and the present study. The simple food matrixes (SS/SS meal with different proteins/fermented wheat roll) had no effect on bioavailable iron measurement with Caco-2 cell model. There is a linear relationship between log absorption ratios in Caco-2 cell model and in human studies (Y = 1.399 X, r2 = 0.9675). Based on our experimental results, it can be concluded that the in vitro digestion/Caco-2 cell model can be used to rank foods with simple and similar food matrixes. To apply the model in mixed food with complicated food matrixes, further studies are needed.